The present invention is directed to a single-use, disposable absorbent laminate containing a nonwoven web bonded to a breathable film. Such laminates have a wide variety of uses, especially in the areas of limited use and disposable items including, but not limited to, surgical and health care related products such as surgical drapes and gowns, disposable work wear such as coveralls and lab coats and personal care absorbent products such as diapers, training pants, incontinence garments, sanitary napkins, bandages, wipes and the like. Many of these products require highly engineered components and yet, at the same time, are required to be limited use or disposable items. By limited use or disposable, it is meant that the product and/or component is used only a small number of times or possibly only once before being discarded.
For example, surgical drapes have been designed to greatly reduce, if not prevent, the transmission of liquids through the surgical drape. In surgical procedure environments, such liquid sources include patient liquids such as blood, saliva and perspiration, and life support liquids such as plasma and saline. In earlier times, surgical drapes were made of cotton or linen. Surgical drapes fashioned from these materials, however, permitted transmission or xe2x80x9cstrike-throughxe2x80x9d of various liquids encountered in surgical procedures. In these instances, a path was established for transmission of biological contaminates, either present in the liquid or subsequently contacting the liquid, through the surgical drape. Additionally, in many instances, surgical drapes fashioned from cotton or linen provided insufficient barrier protection from the transmission therethrough of airborne contaminates. Furthermore, these articles were costly, and of course laundering and sterilization procedures were required before reuse.
Presently, disposable surgical drapes have largely replaced linen surgical drapes. Advances in such disposable surgical drapes include the formation of such articles from liquid absorbent fabrics and/or liquid impervious films which prevent liquid strike-through. For example, see JP 8080318 assigned to Kyowa Hakko Kogyo K K; U.S. Pat. No. 5,546,960 assigned to Molnlycke A B; and WO 96/09165 assigned to Exxon. In this way, biological contaminates carried by liquids are prevented from passing through such fabrics. However, in some instances, surgical drapes formed from absorbent fabrics and/or liquid impervious films sacrifice other drape properties, such as meeting Class 1 flammability requirements per NFPA 702-1980, tear strength, being relatively xe2x80x9clint freexe2x80x9d i.e., not containing loose fibrous elements. Class I flammability requirements are met when a material takes 20 seconds or greater for a flame from a standardized ignition source to spread 5 inches according to NFPA 702-1980 test conditions.
In some instances, surgical drapes fashioned from liquid absorbent fabrics alone, such as fabrics formed from hydrophilic fibers, sufficiently absorb liquids and are more breathable than nonporous materials. However, the breathability provided by such nonwoven fabrics has generally occurred at the expense of liquid barrier properties of the drape. The desire for improved liquid absorptivity and fluid impervious barrier properties has resulted in the lamination of absorbent nonwoven webs to various film or barrier layers. One commercially available application of this configuration is used in the creation of surgical drapes. The surgical drape sold under the tradename Klinidrape(copyright) and assigned to Molnlycke AB, is believed to comprise a liquid absorbent nonwoven top sheet containing inherently hydrophilic rayon staple (discontinuous) fibers, a fluid-impermeable intermediate sheet of polyethylene, a bottom sheet of cellulose, and adhesive components to attach the top and bottom sheets to the polyethylene sheet. Although the above described Klinidrape(copyright) has liquid absorptivity and fluid impermeability, the drape produces relatively numerous lint particles, relies upon adhesive type bonds, and does not pass the Class 1 flammability requirements of NFPA 702-1980.
For such drapes the lamination of nonwoven fabrics to films improves the strength and fluid barrier attributes. Spunbonded fabrics containing continuous synthetic filaments have been laminated with films for consideration in surgical drape applications. Such laminate fabrics do not drastically increase the drape density and are relatively low in cost. One such laminated fabric, comprising a multilayer film bonded to a support layer, such as a hydrophobic spunbonded fabric layer, is disclosed in GB 2296216, which is assigned to Kimberly-Clark Worldwide, and is described as having applications for surgical drapes. However, since the spunbonded fabric component of the above laminate fails to exhibit hydrophilic properties, the drapes made from such laminate fabric lack fluid absorbency.
Another laminate, disclosed in WO 96/09165 and assigned to Exxon, comprises a microporous film adhesively bonded between an outer nonwoven layer containing hydrophobic spunbonded filaments and a hydrophilic nonwoven inner layer. With respect to applications as surgical drapes, the film component provides a barrier to fluid, while the spunbonded component provides strength to the drape. This laminate, however, utilizes adhesive bonding to attach the film to the nonwoven substrate.
Microporous films are well known in the art and in some embodiments typically consist of a film containing some quantity of a particulate filler material dispersed therein. These films with particulate filler material are known as filled films. Under typical processing conditions for making a filled film microporous, the particulate filled films are stretched and/or crushed between compression rollers so as create voids in and around the particles. This renders the films breathable and permits the transmission of water vapor and other gases through micropores developed in and through the film in the regions containing and proximate to the voids while normally inhibiting the transmission of liquids such as water. Filled films treated in the stretching manner typically result in breathable films having water vapor transmission rates of at least 300 grams per square meter per 24 hours (300 g/m2/24 hrs).
One approach to facilitate processing and the subsequent lamination of filled films to other materials constructions is to form surface or xe2x80x9cskinxe2x80x9d layers on one or both sides of the filled film. Frequently these additional film layers have lower amounts of filler content or are monolithic film layers, or are combinations of both. Such multilayered filled films comprise base or xe2x80x9ccorexe2x80x9d layers that contain pore developing fillers and skin layers that optionally contain such pore developing fillers or other fillers and additives. Typically the core layers provide the bulk of the strength and barrier attributes of the entire film while the skin layers contribute but provide additional desired attributes. Stretching and/or crushing processing conditions performed on these films can also render them films breathable. For a multilayered filled film with pore developing fillers in all layers stretching and/or crushing creates voids around the particles as described above and examples of such films are described in U.S. Pat. No. 6,045,900 by Haffiner, et al. For a multilayered filled film with reduced, minimal or with no pore developing fillers present, breathability of the film can be achieved. This is done by proper selection of the polymeric components, their content contribution in each skin, and by appropriate processing of the multilayered film, for example stretching the film so that the skin layers are sufficiently thinned to permit transmission of water vapor and other gases. McCormack, et al, describes examples of such films in U.S. Pat. No. 6,075,179.
One problem has been long recognized and encountered with the above material constructions in thermal lamination to other material constructions. That problem is that known attempts to thermally point bond a nonwoven fabric layer to a microporous thermoplastic film frequently result in a laminate that fails to meet blood strikethrough requirements as described in ASTM-F1670-95. An example of this problem is cited as the comparative example in U.S. Pat. No. 6,238,767 where the use of thermal point bonding to join a multi-layer stretched thinned microporous film to a nonwoven resulted in a laminate that fails the ASTM-F1670-95 test. To surmount this problem U.S. Pat. No. 6,238,767 describes smooth roll calendering techniques that join the microporous film and the nonwoven.
The difficulty in obtaining thermal bonded laminates of nonwovens and microporous films that pass the ASTM-F1670-95 test is further increased when the nonwoven webs are treated with a fugitive surfactants. It is believed that when such webs are thermal bonded to microporous films, some portion of fugitive surfactant present on the web is driven by the heat and pressure of the thermal bonding process into the film itself at the bond areas. When liquid such as water, blood, or urine contacts this surfactant present in the microporous regions of the film the surface tension of the liquid decreases sufficiently to result in the passage of liquid through the microporous network. Such laminates fail to pass the blood strikethrough criteria set forth in ASTM-F1670-95. It is believed that the pressures and temperatures used in the thermal bonding process create intimate contact among the surfactant, the polymers of the nonwoven fabric, and the polymers and other materials present in the film at bonded regions. This is believed to result in the presence of surfactant in the microporous regions that reduces the surface tension of liquid that contacts these regions and allows the liquid to pass through the laminate.
A common technique used to negate the effect of surfactant contamination in the film is to avoid it altogether by attaching the film via an adhesive to the surfactant treated nonwoven web. So long as the bond is non-thermal and the film and surfactant treated nonwoven are physically separated, surface tension reduction of liquids in the microporous regions is eliminated or at least minimized. An alternative technique is to thermally bond the film to a surfactant free web. Once the bond is established, as a subsequent step, the film/nonwoven laminate can be topically treated with the surfactant to be rendered hydrophilic. U.S. Pat. No. 5,901,706 by Griesbach, et al, describes such laminates, made by adhesive attachment or by thermal bonding followed by surfactant treatment, suitable for surgical drapes.
Consequently, until the present invention, it was believed that microporous films thermally bonded to nonwoven webs with surfactant treatments could not reliably provide the liquid barrier necessary to enable the film/nonwoven laminate to pass the blood strikethrough criteria of ASTM-F1670-95.
The present invention is drawn to a disposable, absorbent laminate containing one or more layers of surfactant-treated meltspun nonwoven thermally bonded to a breathable film and a method of making the same. Such a laminate is useful for surgical drapes and would have applications for gowns, disposable work wear such as coveralls and lab coats and personal care absorbent products such as diapers, training pants, incontinence garments, sanitary napkins, bandages, wipes and the like. In accordance with the invention the laminate should provide superior liquid absorptivity, exhibit relatively low levels of lint particles, pass the blood strikethrough criteria of ASTM-F 1670-95, meet the Class 1 flammability requirements of NFPA 702-1980, and maximize drape strength all at a relatively low cost. As such, the present invention is drawn to a laminate comprising a nonwoven web having been treated with a surfactant and a stretched film. The stretched film comprises a core layer and at least one skin layer. The core layer has a percentage by weight of a micropore developing filler material incorporated therein. The stretched film has been stretched in at least one direction to some percentage of its original size until a desired degree of vapor permeability is reached. The film is thermally bonded to the surfactant treated nonwoven. The end result is a laminate that forms both a breathable barrier and passes blood strikethrough in compliance with ASTM F1670-95 and has an exposed face that is capable of absorbing aqueous liquids.
In another embodiment, the invention is drawn to a breathable absorbent laminate compliant with ASTM F1670-95. The laminate comprises a nonwoven web treated with a surfactant. The nonwoven web is thermally bonded at a plurality of bond points to a multilayer polyolefin resin film, at least some of the bond points form attachments between the web and the multilayer film. At least one layer of the multilayer film contains a percentage by weight of a micropore developing filler.
In other embodiments, the invention is a surgical drape consisting of a thermally bonded laminate made from a stretched multilayered filled film and a surfactant treated, hydrophilic and absorbent meltspun nonwoven web.
The laminates of the present invention satisfy the need in the art for materials that provide improved liquid absorptivity while passing blood strikethrough criteria set fort in ASTM-F1670-95, as well as, providing comfort, improved drape strength, and having relative low levels of lint particles, while meeting the Class 1 flammability requirements of NFPA 702-1980 (flame propagation of 20 seconds or greater).
The laminates of the present invention may be formed from thermal bonding a film that contains at least one microporous layer and one or more nonwoven fabric layers so as to include at least one layer of hydrophilic meltspun fabric. In general, the filaments of the contemplated nonwoven fabrics are made from hydrophobic polymeric material. These materials are made hydrophilic by treating with a hydrophilic chemical additive, such as a surfactant, in or on the filaments.